http://www.webmd.com/multiple-sclerosis/news/20090428/high-doses-vitamin-d-cut-ms-relapses?page=2

Vitamin D appears to suppress the autoimmune responses thought to cause MS, Burton says. In MS, haywire T lymphocytes -- the cellular "generals" of the immune system -- order attacks on the myelin sheaths that surround and protect the brain cells.

In people given high-dose vitamin D in the study, T cell activity dropped significantly. That didn't happen in people who took lower doses.

The researchers also measured the concentration of 25-hydroxyvitamin D [25(OH)D], also known as calcidiol, in the blood. The Institute of Medicine says that is the best indicator of a person's vitamin D status.

There's no ideal level, although concentrations of less than 50 nanomoles per liter of blood are considered inadequate for good health. In the study, it appeared MS patients did best if levels reached 100 nanomoles per liter, Burton says.

People with MS should talk to their doctors about whether they might benefit from vitamin D supplements, she says.

"Too much vitamin D can be harmful for people with certain medical conditions such as kidney disease," Burton says. "Also doctors can monitor your blood levels of 25(OH)D."

http://www.webmd.com/multiple-sclerosis/news/20090428/high-doses-vitamin-d-cut-ms-relapses?page=2